What are Astral Diamonds made of?

Question

In any edition of Dungeons and Dragons, or in any related fiction in any campaign setting, is there official word for what Astral Diamonds actually are? Lacking that, any hints or clues in any published work? Presumably they are diamonds from the astral plane, but given that the astral plane is not exactly like the prime material plane, it's got to be pretty weird.

Are they condensed magic? Crystalized thoughts? Souls?

Or is there no lore on them at all, and a requirement that each DM make it up for themselves?

I know astral diamonds became standard official currency in 4th edition, but I'm nigh-certain they existed in 3rd edition, if not 2nd. I can't FIND information about it, hence asking the question, but I'm so sure people at my local gaming store and college referenced astral diamonds as bargaining chips for diabolic deals back in 3rd edition, and my vague memory tells me either planescape or spelljammer was the source.

Answer 1

They're the foundation stones of the fallen Lattice of Heaven*.

*Some** say.

_{**Completely uncredited speculation in a sidebar on p. 36 of The Plane Above.}

For all the flak 4E tends to catch for the way it rewrote the cosmos, it mostly made big broad strokes and left the rest undefined for the GM to fill in as they suit. Like, it's not saying that astral diamonds are being deliberately placed in circulation so that when the Game of Making rediscovers the secret of the Lattice of Heaven in Hestavar, there'll already be a critical mass of raw material to reconstruct the thing, assembled and brought there voluntarily out of self-interest and ambition. But it's not not saying that, you get me?

Astral Diamonds: Origins

As a means of exchange, astral diamonds absolutely originate in 4E. 3E's solution to players needing giant piles of money in the Epic Level Handbook was essentially a system of promissory notes called favors, operating on the principle that hiring someone to cast a spell for you had predictable pricing. (Epic Level Handbook p.114, "Managing Wealth".)

This is not to say nobody ever put the words "astral" and "diamond" together before then. Like, look: chaos pearls, fey rubies, shadow sapphires. Doesn't that fire you up to go collect some of those? And I'm pretty sure I just made all of them up.

But as the highest form of currency, the 10,000 gold piece, they made their debut in 4E, on the PHB p.212, "Coins and Currency".

Astral Diamonds: Fun Facts

• Actual "fancy carbon"-style diamonds are prized for their colorlessness and clarity, like pure water. Are astral diamonds held to the same standard, or are they prized for their likeness to the "waters" of the Astral Sea?
• Astral diamonds weigh 10 to the gold piece, so one pound of astral diamonds contains 500 astral diamonds, or 5,000,000 gold pieces - more than enough to buy any magic item that moves on the open market, since level 30s top out at a little over 3 million.
• As treasure (4E DMG p.124), astral diamonds start showing up in loot parcels beginning at level 24, in tens and twenties. However, it's also noted that they are gems in their own right, and while there's no 10,000 gp gem slot, it's easy enough to imagine them taking the place of two 5,000 gp gems, or serving as the centerpiece gem or gems to a suitably valuable piece of art, putting singleton astral diamonds well within the bounds of possibility to encounter as early as level 14.

Astral Diamonds: Made of Residuum, Because Numbers? (No.)

You can find this sentiment all over blogs and message boards from the early days of 4E: astral diamonds must be made of residuum since the same weight is worth the same amount. The equivalence is simple, satisfying, and, sadly, wrong.

Residuum was also introduced in 4E (PHB 225), as the aftermath of the Disenchant Magic Item ritual and a universally useful ritual ingredient in its own right. One gold-piece weight of residuum is worth 10,000 gp, which sounds like a lot, and it absolutely is, but high-end rituals like the level 28 True Portal will run you 50,000 gp a shot.

A gold-piece weight of residuum is 10,000 gp, and an astral diamond is 10,000 gp, but a gold-piece weight of astral diamonds is 10 astral diamonds, or 100,000 gp. The equivalence is a lot less easy to draw when it's off by an order of magnitude.

If you wanted to you could still go for it, of course. Gemstones have value in their cut and clarity - a cut diamond is worth more than an equivalent mass of diamond dust. But that's just an "if you wanted to", and you can want a lot of things.

Astral Diamonds: Powered By A Forsaken Child? (Also no.)

That same sidebar on p.36 of The Plane Above notes they're mined primarily in Celestia and Hestavar, the two major good-aligned domains. Tearing up souls for monetary gain is absolutely something the other domains would more actively pursue if they were able. And while it is noted in The Plane Above that many outsiders, those dead failed by the Lattice of Heaven, will often immure themselves in the border islands as they fade away, that's just regular stone - those souls that can get into a celestial domain have another destination; for example, souls in Celestia head for Chronias and depart to an unknown destiny across the Bridge of al-Sihal.

Answer 2

To my knowledge:

1. Astral diamonds existed exclusively in 4E (it's definitely the only edition where they're a standardized unit of currency). I've seen people claim to remember them existing prior to 4E, often in Planescape like you say, but they don't appear in the core campaign setting for 2E, nor the Manual of the Planes or the Planar Handbook for 3E/3.5E; if they existed, it was in some niche 2E Planescape supplement (and I own quite a lot of those, and have no memory of them, though I won't claim that's definitive). It wouldn't make sense pre-4E in Spelljammer, which had no reason to have a unique tie to the Astral in it (there was no 3E Spelljammer, and 2E Spelljammer took place entirely within the Prime Material Plane, it had no particular connection to the Astral; 4E Spelljammer introduced the idea that spelljammer helms allow planar travel, and 5E officially replaced the Phlogiston with the Astral). The Manual of the Planes for 4E happens to mention them in passing, and I could easily see someone mixing up memories of two editions when the book has the same name, but AFAICT, no D&D-related reference to "astral diamond" occurred prior to June, 2008 when 4E released, nor "astral diamonds" for that matter (the few hits that seem to occur before '08 are clearly misdated, and refer to 4E or the Neverwinter game currency). Without that date filter, all the references I can find that refer to 2E or 3E/3.5E are either:

   • Other people with vague memories like yours (but all of those posts are from 2014 and later, long after 4E could have corrupted their memory), or
   • Various homebrew pages (all of which post-date 4E, and likely borrowed the term from there)

2. Very little lore has been published on them beyond the 4E PHB and DMG AFAICT. They were just a way to make it possible to cart around huge amounts of money without worrying about encumbrance (4E made platinum worth 100x as much as gold, and astral diamonds worth 100x as much as platinum, and astral diamonds weighed one-tenth what other coins weighed to boot, so astral diamonds let you cart around 100,000 GP worth of value with the encumbrance of a single gold coin, 5 million GP of value per pound of astral diamonds; even the party wizard could carry the party loot if it was condensed that much).

The 4E PHB says nothing of substance about them (just that they're used in major planar marketplaces for "transactions involving staggering amounts of wealth"), without specifying a single attribute beyond weight and value.

The 4E DMG adds that they are "clear, faceted gems that glow with a faint silvery light", and that they are mined specifically in divine dominions floating through the Astral Sea, especially in Mount Celestia and the hinterlands of the Bright City, and that abandoned divine dominions may have them, but they're poor sources of astral diamonds (this implies a divine origin, but the nature of it is unclear). It also specifies that they're usually found in strings of 5-10 diamonds, linked with mithril or silver.

The Plane Above: Secrets of the Astral Sea mentions them in passing, but mostly repeats what the DMG said, adding only that they "are thought by some to be side effects of the destruction of the Lattice of Heaven." (some vague prehistory attempt by the gods to link all their dominions into a single realm, that was shattered before completion in the Primordial War)

From the fact that they are currency, you can deduce some things about them. They're clearly not like normal diamonds, which come in all shapes and sizes and are essentially impossible to reduce to a quasi-uniform shape and value required for a currency. Presumably astral diamonds form (or are artificially created) in some extremely uniform way that makes them suitable for currency in their natural state, or they're much more uniform in consistency than diamonds and much more easily cut up into a uniform currency size than gems are (if they were like normal gems, they'd presumably be kept intact to preserve value, and imperfections and color differences would affect value). It's up to the DM what they want them to be, whether it's crystalized magic, some residue of the souls or thoughts that pass through the Astral Plane, some condensed residue of good/law or both (Mount Celestia being the primary source may imply a connection to alignment), or simply a product of a (presumably rare, exceedingly dangerous, or both) creature. 4E wasn't big on fluff (probably the single most-fluff-free edition since at least AD&D 1E), you get to make it up yourself.